1. Field of the Invention
This invention relates to a fuel supply system for an engine, and more particularly to an improved fuel supply system for an engine having multiple charge formers.
2. Description of the Related Art
Many internal combustion engines are provided with a plurality of charge formers. With such an arrangement, it is desirable to ensure that the fuel supply system delivers fuel uniformly and equally to all of the charge formers. Although this is generally not a problem, with certain types of applications for internal combustion engines, it can become a problem.
For example, with some applications for internal combustion engines, the charge formers are disposed so that they are positioned vertically above each other. This is typical, for example, in outboard motor practice. In outboard motors, the engine is disposed so that its output shaft rotates about a vertically extending axis. As a result, the individual cylinders extend generally horizontally and are arranged in a vertically spaced relationship. The charge formers, therefore, adopt a similar attitude and disposition.
Fuel supply systems for engines with vertically-arranged charge formers frequently include a single conduit or manifold that extends from the fuel pump to all charge formers. The conduit may be configured in such a way that it forms areas where fuel or vapor can become trapped. Additionally, the fuel pump itself may be configured in such a way that it forms areas where fuel vapor can be trapped. If a fuel vapor pocket forms, then the charge formers downstream of the vapor pocket will not receive fuel, or at least not receive a desired amount of fuel, thereby affecting proper engine operation.
In an attempt to alleviate these problems, it has been proposed to provide the fuel pump at a lower location than the charge formers. Also, the fuel pump may be provided with a plurality of fuel outlets and conduits that feed respective carburetors of the system. With this type of arrangement, however, the fuel pump is normally positioned below the lowest carburetor. In this position, the relatively high head between the fuel pump and the highest carburetor restricts the fuel pump's ability to deliver fuel. Also, vapor venting is not assured. Furthermore, a fuel pump mounted below the lowest carburetor may not be capable of being powered by an engine camshaft.
Accordingly, a need exists for a fuel supply system for an engine having multiple charge formers, wherein the system ensures against vapor blockage in fuel supply lines. There is a further need for a fuel system having a fuel pump which is powered by a camshaft, the fuel pump being arranged to prevent vapor interference with fuel flow.